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From: Thomas Hellstrom <thellstrom@vmware.com>
To: "hch@lst.de" <hch@lst.de>,
	"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Deepak Singh Rawat <drawat@vmware.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>
Subject: Re: revert dma direct internals abuse
Date: Mon, 8 Apr 2019 18:47:52 +0000	[thread overview]
Message-ID: <7d5f35da4a6b58639519f0764c7edbfe4dd1ba02.camel@vmware.com> (raw)
In-Reply-To: <20190408105525.5493-1-hch@lst.de>

Christoph,


On Mon, 2019-04-08 at 12:55 +0200, Christoph Hellwig wrote:
> Hi Linus,
> 
> unfortunately it took less than a merge window for the:
> 
> /*
>  * All the dma_direct_* declarations are here just for the indirect
> call bypass,
>  * and must not be used directly drivers!
>  */
> 
> warning in dma-mapping.h to be ignored.  This series reverts the
> offender
> to keep our API clean.
> 
> Thomas: please talk me first about your needs and I'll be happy to
> figure out
> a proper API for what you want to do.

We HAVE discussed our needs, although admittedly some of my emails
ended up unanswered.

We've as you're well aware of had a discussion with the other
subsystems doing user-space DMA-buffers wanting this functionality from
the dma api (AMD graphics and RDMA people IIRC). that is a bool that
tells us whether streaming dma mappings are coherent, and I described
in detail why we couldn't use the dma_sync_* API and
dma_alloc_coherent().

The other option we have is to just fail miserably without messages if
streaming DMA is not coherent, which I think the other drivers might
do... That's all I'm trying to avoid here. I'd much prefer to have the
dma API export this bool.

/Thomas







WARNING: multiple messages have this Message-ID (diff)
From: Thomas Hellstrom via iommu <iommu@lists.linux-foundation.org>
To: "hch@lst.de" <hch@lst.de>,
	"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>
Cc: "iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Deepak Singh Rawat <drawat@vmware.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: revert dma direct internals abuse
Date: Mon, 8 Apr 2019 18:47:52 +0000	[thread overview]
Message-ID: <7d5f35da4a6b58639519f0764c7edbfe4dd1ba02.camel@vmware.com> (raw)
Message-ID: <20190408184752.s-De-chLsHCCgj-edAKrgehuXwkxHs-kHd6kGS3jGrU@z> (raw)
In-Reply-To: <20190408105525.5493-1-hch@lst.de>

Christoph,


On Mon, 2019-04-08 at 12:55 +0200, Christoph Hellwig wrote:
> Hi Linus,
> 
> unfortunately it took less than a merge window for the:
> 
> /*
>  * All the dma_direct_* declarations are here just for the indirect
> call bypass,
>  * and must not be used directly drivers!
>  */
> 
> warning in dma-mapping.h to be ignored.  This series reverts the
> offender
> to keep our API clean.
> 
> Thomas: please talk me first about your needs and I'll be happy to
> figure out
> a proper API for what you want to do.

We HAVE discussed our needs, although admittedly some of my emails
ended up unanswered.

We've as you're well aware of had a discussion with the other
subsystems doing user-space DMA-buffers wanting this functionality from
the dma api (AMD graphics and RDMA people IIRC). that is a bool that
tells us whether streaming dma mappings are coherent, and I described
in detail why we couldn't use the dma_sync_* API and
dma_alloc_coherent().

The other option we have is to just fail miserably without messages if
streaming DMA is not coherent, which I think the other drivers might
do... That's all I'm trying to avoid here. I'd much prefer to have the
dma API export this bool.

/Thomas






_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  parent reply	other threads:[~2019-04-08 18:47 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-08 10:55 revert dma direct internals abuse Christoph Hellwig
2019-04-08 10:55 ` Christoph Hellwig
2019-04-08 10:55 ` [PATCH] Revert "drm/vmwgfx: Improve on IOMMU detection" Christoph Hellwig
2019-04-08 10:55   ` Christoph Hellwig
2019-04-08 20:05   ` Thomas Hellstrom
2019-04-08 20:05     ` Thomas Hellstrom via iommu
2019-04-08 20:05     ` Thomas Hellstrom via iommu
2019-04-08 18:47 ` Thomas Hellstrom [this message]
2019-04-08 18:47   ` revert dma direct internals abuse Thomas Hellstrom via iommu
2019-04-09  9:57   ` hch
2019-04-09  9:57     ` hch
2019-04-09 13:04     ` Thomas Hellstrom
2019-04-09 13:04       ` Thomas Hellstrom via iommu
2019-04-09 13:04       ` Thomas Hellstrom via iommu
2019-04-09 13:31       ` hch
2019-04-09 13:31         ` hch
2019-04-09 14:17         ` Thomas Hellstrom
2019-04-09 14:17           ` Thomas Hellstrom via iommu
2019-04-09 15:25           ` hch
2019-04-09 15:25             ` hch
2019-04-09 17:24             ` Thomas Hellstrom
2019-04-09 17:24               ` Thomas Hellstrom via iommu
2019-04-09 17:24               ` Thomas Hellstrom via iommu
2019-04-10  6:43               ` hch
2019-04-10  6:43                 ` hch
2019-04-10 15:01                 ` Thomas Hellstrom
2019-04-10 15:01                   ` Thomas Hellstrom via iommu
2019-04-10 15:01                   ` Thomas Hellstrom via iommu
2019-04-22 17:56                   ` hch
2019-04-22 17:56                     ` hch
2019-04-22 17:56                     ` hch-jcswGhMUV9g
2019-04-23 12:26                     ` Thomas Hellstrom
2019-04-23 12:26                       ` Thomas Hellstrom via iommu

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